Modern reconnaissance/attack aircraft are designed with various on-board systems for conducting intelligent automated search of the terrain being overflown. These systems are designed to minimize the burden on the flight crew when making tactical decisions by analyzing the vast amount and constantly changing sources of data associated with the aircraft's current state. For example, conventional navigation systems, particularly those employing GPS, provide real time, three dimensional coordinates in the near earth airspace where the aircraft is operating. Digital database maps provide aircraft personnel with detailed terrain data in the vicinity of the aircraft.
Today's aircraft also include target acquisition systems (TAS) that provide range, resolution, fast scanning and computerized detection and classification of targets/threats around the aircraft. These systems are designed to search large surface areas in very short times.
The primary drawback to conventional aircraft search/scanning systems is the ability to recognize both the constraints and requirements of the information provided. For example, current target acquisition systems do not take into account system constraints, such as clear line of sight, TAS turret rotational velocities and accelerations, image processing rates, aircraft velocity and height above terrain. The conventional systems also do not take into account the mission requirements, such as expected threat capabilities and the nature of a mission (e.g., reconnaissance, assault or recovery). Only when the constraints and requirements are balanced in real time can the terrain search be optimized for mission goals, whether those goals are information gathering, survivability or time of transit.
FIG. 1 illustrates a conventional automatic scanning technique, such as a target detection system, as used in present day aircraft. The aircraft scans the terrain with either a single or two bar sweep defined by triangular zone A. (A single scan generally uses a preset set mid-range scan of the terrain to determine what is in front of the aircraft. A two bar scan uses both a long range scan and a short range scan to image the terrain). Once elevation and azimuthal limits are programmed into the system, the turret is locked into a scan pattern that can only compensate for aircraft pitch attitude changes, i.e., if the aircraft pitches downward, the TAS adjusts upward to maintain constant azimuthal and elevational scan limits. The conventional systems are not able to automatically compensate for variations in terrain or changes in tactical situations.
Often, due to the low altitude regime that helicopters operate in and because of rolling terrain, the aircraft will come upon terrain that quickly slopes down or up. In these cases, without intervention from the pilot, gaps occur in the terrain being searched. In the case of down slopes, due to fixed elevation limits, the aircraft could easily overfly the depression without ever detecting whether targets of interest are located in the area. The deficiency in the prior scanning system is illustrated in FIG. 1A where the forward looking scan from the aircraft does not detect the bottom of the depression (the shaded area). Similarly, an up sloped region, such as a hill shown in FIG. 1B, results in decreased detection range since the fixed elevation limits cause the sensor to look into a hillside rather than scanning upwards to the hill crest. As such, the aircraft will not detect a threat at the top of the hill until the aircraft is almost upon it. Also, as the scan passes over the crest, the vertical elevation of the hill obscures a portion of the terrain directly behind it. This poses another threat to the aircraft.
A need therefore exists for an automated search system that takes into account system constraints and requirements.